DE102010046142A1 - Modular switch for an electrical converter, electrical converter and method for operating an electrical converter - Google Patents

Abstract

A modular switch (10) for an electrical converter is described. The modular switch (10) is provided with a first series circuit consisting of a first controllable power semiconductor component (V1) and a first diode (D1) and with a second series circuit consisting of a second diode (D2) and a second controllable power semiconductor component (V2). The connection point of the first power semiconductor component (V1) and the first diode (D1) forms a first connection (11) and the connection point of the second diode (D2) and the second power semiconductor component (V2) forms a second connection (12) of the modular switch (10) , 20). A capacitor (C) is provided, the first series circuit and the second series circuit and the capacitor (C) being connected in parallel to one another.

Description

The invention relates to a modular switch for an electrical converter, an electrical converter and a method for operating an electrical converter.

An inverter is an electrical circuit designed to transform electrical energy. For intermediate storage of the electrical energy, a DC voltage applied to a DC link is present, which is usually constructed of one or more capacitors. Parallel to the intermediate circuit, for example, two series-connected, controllable switches are present for each phase of the alternating voltage, each of which can be assigned a freewheeling diode. These switches are controlled in such a way that an alternating voltage can be tapped off at the connection points of the switches.

By way of example, such a converter may be a rectifier or an inverter or, more generally, a power converter.

From the DE 101 03 031 A1 is a converter circuit is known, which is constructed per phase of a plurality of series-connected, similar subsystems. Each subsystem has a capacitor to which two series-connected, controllable switches, each with a freewheeling diode are connected in parallel. The capacitors of the subsystems of one phase thus form the intermediate circuit for this phase.

A disadvantage of the known converter circuit is that the capacitors in the individual subsystems usually do not have the same state of charge, so that the voltages at the intermediate circuits of the phases are not the same. This results in operation, d. H. when the switches are switched on, to transhipment operations with resulting oscillatory currents between the phases.

The object of the invention is to provide an electrical converter which does not have the disadvantages of the prior art.

The invention solves this object by a modular switch for an electrical converter according to claim 1, by an electrical converter according to claim 9 and by a method for operating an electrical converter according to claim 12.

The modular switch according to the invention is provided with a first series circuit consisting of a first controllable power semiconductor component and a first diode and with a second series circuit consisting of a second diode and a second controllable power semiconductor component. The connection point of the first power semiconductor device and the first diode forms a first terminal and the connection point of the second diode and the second power semiconductor device forms a second terminal of the modular switch. A capacitor is provided, wherein the first series circuit and the second series circuit and the capacitor are connected in parallel to each other.

The electrical converter according to the invention is provided for converting a two- or multi-phase AC voltage into a controllable DC voltage or vice versa. The converter is provided with a plurality of the aforementioned modular switches, wherein for each phase of the AC voltage at least two modular switches are connected in series. The controllable DC voltage can dynamically assume positive as well as negative values via the switching states of the individual modular switches.

The modular switch according to the invention is designed only for one direction of current. In the opposite direction of the current, the power semiconductor components block the flow of current. Thus, the current direction is not reversible in the inverter according to the invention. This has the advantage that - if any - only compensating currents between the phases of the inverter can occur, but no oscillating currents.

In the method according to the invention, the power semiconductor components of the phases of the converter are switched such that deviations of the voltages at the intermediate circuits of the phases formed by the capacitors are reduced. This makes it possible to influence the voltages at the intermediate circuits formed by the capacitors of the phases of the inverter so that they are about the same size, so that the deviations of these voltages are minimized. In this way, equalizing currents between the individual phases of the inverter can be avoided.

In an advantageous embodiment of the invention, the terminal voltage is substantially equal to the negative or positive DC voltage when both power semiconductor devices are turned off or turned on or it is the terminal voltage substantially equal to zero when one of the two power semiconductor devices is turned off and the other is turned on. In this way, it is advantageously possible that the terminal voltage is either substantially equal to the negative DC voltage or is substantially equal to the positive DC voltage or substantially equal to zero.

It is particularly expedient if the power semiconductor components in each case a freewheeling diode is connected in parallel. This serves to protect the power semiconductor components.

If, for example, IGBTs (IGBT = Insulated Gate Bipolar Transistor) are used as power semiconductor components, then they have only limited blocking capability. In this case, it may be necessary to increase the blocking capability of the individual IGBTs by another series-connected diode. It is also possible to connect the individual IGBTs each with an antiparallel freewheeling diode. In the latter case, although a current flow in the negative direction is possible, but this current flow only leads to a charging of the capacitor to the applied terminal voltage. After that, the flow of electricity stops and the transfer process is finished. Thus, with free-wheeling diodes, it is also possible to avoid oscillating currents between the phases of an inverter constructed from a plurality of modular switches.

With the aid of the modular switches according to the invention, almost any multi-level or multipoint converters can be constructed in a modular manner. For example, multi-level converters with three or five operating points can be realized with the aid of the modular switches according to the invention. Due to the modular structure of the effort and thus the cost of implementing such multi-level converters are reduced.

Other features, applications and advantages of the invention will become apparent from the following description of embodiments of the invention, which are illustrated in the accompanying figures. All described or illustrated features, alone or in any combination form the subject matter of the invention, regardless of their summary in the claims or their dependency and regardless of their formulation or representation in the description or in the drawing.

1 shows an electrical circuit diagram of an embodiment of a modular switch for an electrical converter, 2 shows the wiring diagram of 1 with added components, and 3 and 4 each show an electrical circuit diagram of an embodiment of an electrical converter using the modular switch of 2 ,

In the 1 is a modular switch 10 illustrated, which is intended for use in an electrical converter.

The modular switch 10 has a first series circuit consisting of a first controllable power semiconductor device V1 and a first diode D1 and a second series circuit consisting of a second diode D2 and a second controllable power semiconductor device V2.

The two controllable power semiconductor components V1, V2 can each have a diode connected in series for the purpose of increasing the blocking capability.

In the first series connection, the collector of the first power semiconductor device V1 and the anode of the first diode D1 are connected together. This connection point is the first connection 11 designated. In the second series circuit, the emitter of the second power semiconductor device V2 and the cathode of the second diode D2 are connected together. This connection point is the second connection 12 designated.

The two series circuits are connected in parallel with each other. Thus, the cathode of the first diode D1 is connected to the collector of the second power semiconductor device V2 and the emitter of the first power semiconductor device V1 is connected to the anode of the second diode D2.

To the two series circuits connected in parallel, a capacitor C is connected in parallel.

On the capacitor C is a DC voltage u _dc and between the two terminals 11 . 12 is a terminal voltage u _a available. The direction of the above voltages is in the 1 specified. Continue to flow from the first port 11 a current i towards the second terminal 12 ,

The power semiconductor components V1, V2 are controllable switches, for example transistors, in particular field effect transistors, or thyristors with optionally required auxiliary circuitry, in particular GTO thyristors (GTO = gate turn off), or IGBTs (IGBT = insulated gate bipolar transistor ), or comparable electronic components. Depending on the configuration of the power semiconductor components V1, V2, the terminals of the same may have different names. The above designations collector and emitter refer to the exemplary use of IGBTs. The capacitor C may be formed unipolar.

• – Wenn die Leistungshalbleiterbauelemente V1, V2 beide ausgeschaltet (sperrend) sind, dann fließt der Strom i von dem ersten Anschluss 11 über die Diode D1, über den Kondensator C und über die Diode D2 zu dem zweiten Anschluss 12. Der Kondensator C wird von diesem Strom i geladen, so dass die Gleichspannung u_dc größer wird. Abgesehen von den Spannungsabfällen an den Dioden D1, D2 ist die Anschlussspannung u_a gleich der negativen Gleichspannung –u_dc, also u_a = –u_dc.
• – Wenn die Leistungshalbleiterbauelemente V1, V2 beide eingeschaltet (leitend) sind, dann fließt der Strom i von dem ersten Anschluss 11 über das erste Leistungshalbleiterbauelement V1, über den Kondensator C und über das zweite Leistungshalbleiterbauelement V2 zu dem zweiten Anschluss 12. Der Kondensator C wird von diesem Strom i entladen, so dass die Gleichspannung u_dc kleiner wird. Abgesehen von den Spannungsabfällen an den Leistungshalbleiterbauelementen V1, V2 ist die Anschlussspannung u_a gleich der positiven Gleichspannung u_dc, also u_a = u_dc.
• – Wenn das erste Leistungshalbleiterbauelement V1 eingeschaltet (leitend) und das zweite Leistungshalbleiterbauelement V2 ausgeschaltet (sperrend) ist, dann fließt der Strom i von dem ersten Anschluss 11 über das erste Leistungshalbleiterbauelement V1 und über die zweite Diode D2 zu dem zweiten Anschluss 12. Die Gleichspannung u_dc an dem Kondensator C bleibt konstant. Abgesehen von den Spannungsabfällen an dem ersten Leistungshalbleiterbauelement V1 und der zweiten Diode D2 ist die Anschlussspannung u_a gleich Null, also u_a = 0.
• – Wenn das erste Leistungshalbleiterbauelement V1 ausgeschaltet (sperrend) und das zweite Leistungshalbleiterbauelement V2 eingeschaltet (leitend) ist, dann fließt der Strom i von dem ersten Anschluss 11 über die erste Diode D1 und das zweite Leistungshalbleiterbauelement V2 zu dem zweiten Anschluss 12. Die Gleichspannung u_dc an dem Kondensator C bleibt konstant. Abgesehen von den Spannungsabfällen an der ersten Diode D1 und dem zweiten Leistungshalbleiterbauelement V2 ist die Anschlussspannung u_a gleich Null, also u_a = 0.

The modular switch 10 can take four states:

• When the power semiconductor devices V1, V2 are both off (blocking), then the current i flows from the first terminal 11 via the diode D1, via the capacitor C and via the diode D2 to the second terminal 12 , The capacitor C is charged by this current i, so that the DC voltage u _dc becomes larger. Apart from the voltage drops across the diodes D1, D2, the terminal voltage u _{a is} equal to the negative DC voltage -u _dc , so u _a = -u _dc .
• When the power semiconductor devices V1, V2 are both turned on (conducting), then the current i flows from the first terminal 11 via the first power semiconductor component V1, via the capacitor C and via the second power semiconductor component V2 to the second terminal 12 , The capacitor C is discharged from this current i, so that the DC voltage u _{dc is} smaller. Apart from the voltage drops across the power semiconductor components V1, V2, the terminal voltage u _{a is} equal to the positive DC voltage u _dc , ie u _a = u _dc .
• When the first power semiconductor device V1 is turned on (conducting) and the second power semiconductor device V2 is off (blocking), then the current i flows from the first terminal 11 via the first power semiconductor component V1 and via the second diode D2 to the second terminal 12 , The DC voltage u _dc on the capacitor C remains constant. Apart from the voltage drops across the first power semiconductor device V1 and the second diode D2, the terminal voltage u _{a is} equal to zero, ie u _a = 0.
• When the first power semiconductor device V1 is turned off (blocking) and the second power semiconductor device V2 is turned on (conducting), then the current i flows from the first terminal 11 via the first diode D1 and the second power semiconductor device V2 to the second terminal 12 , The DC voltage u _dc on the capacitor C remains constant. Apart from the voltage drops at the first diode D1 and the second power semiconductor component V2, the terminal voltage u _{a is} equal to zero, ie u _a = 0.

The current i through the modular switch 10 is always in the same direction. This direction is predetermined by the diodes D1, D2. The terminal voltage u _a can assume essentially three values, namely u _a = -u _dc or u _a = u _dc or u _a = 0. The DC voltage u _{dc across} the capacitor C can become larger or smaller.

In the 2 is a modular switch 20 shown, all the components of the modular switch 10 of the 1 and, in terms of its circuitry with the modular switch 10 of the 1 matches. Matching components of the modular switch 20 of the 2 are therefore characterized in the same way as in the modular switch 10 of the 1 , In that regard, reference is made to the above description of the modular switch 10 of the 1 directed.

In addition to the modular switch 10 of the 1 has the modular switch 20 of the 2 one freewheeling diode each 21 to the two power semiconductor devices V1, V2. It is expressly noted, however, that these freewheeling diodes 21 in itself for the operation of the modular switch 20 of the 2 not required are the modular switch 20 without the freewheeling diodes 21 - So in the basis of the modular switch 10 of the 1 explained manner - is fully functional.

In practice, however, you will freewheeling diodes 21 to protect the power semiconductor devices V1, V2 provide. With the help of free-wheeling diodes 21 possible damage to the power semiconductor devices V1, V2 can be prevented in an unwanted current direction reversal of the current i.

Normally, the current i flows in the positive direction of the in the 2 indicated streaming file. However, if the current i reverses, it flows through the free-wheeling diodes 21 , The terminal voltage u _a becomes u _a = + u _dc and the capacitor C is charged. In this case, the switching state of the power semiconductor devices V1, V2 does not matter.

Furthermore, with the help of freewheeling diodes 21 can be achieved that on the capacitor C no voltage reversal can occur, so that - if desired - a unipolar capacitor can be used.

In the 3 is an electrical inverter 30 pictured using the modular switch 20 of the 2 is constructed. It is a so-called multi-level or multi-point converter, which in the present case the 3 has three operating points.

The inverter 30 is exemplified for the connection of a three-phase AC voltage, wherein the respective components of the three phases are marked with I, II, III. It is understood that the inverter 30 may also be formed in two phases or more generally multiphase.

Every phase of the inverter 30 are two modular switches 20 assigned.

As with the phase III of the inverter 30 shown is the connection 11 the first, upper switch 20 with the connection 12 the second, lower switch 20 connected. Furthermore, the connection 12 the first, upper switch 20 via a first DC link inductance 31 with a positive pole + and the connection 11 the second, lower switch 20 via a second DC link inductance 32 with a negative pole - connected. It is also possible that only one of the two DC link inductances 31 . 32 is available.

Between the positive and the negative terminal is a DC voltage. The DC voltage may have different values and may in particular be positive or negative. The DC voltage can also be generated by another inverter, the inverter 30 of the 3 is switched counter. This other inverter can be the same as the inverter 30 be educated.

The connection point of the two modular switches 20 is via an inductance 33 led to a terminal P, at which abut the phases of the AC voltage.

Each of the modular switches 20 is via a parasitic inductance with the DC link inductances 31 . 32 connected. These parasitic inductances can also be formed discretely. The parasitic inductances are particularly helpful for limiting the current during possible compensation processes.

With regard to the other two phases I, II is the inverter 30 constructed accordingly. The inductors 33 The three phases can then be realized for example by a three-phase reactor. The inductors 33 but can also be realized by a connected inductive load or a transformer.

As has been explained, the terminal voltage u _{a of} each modular switch 20 essentially assume three states: u _a = -u _dc or u _a = u _dc or u _a = 0. Thus, the voltage of each phase of the terminal P relative to the plus or the negative pole also substantially assume these three aforementioned states.

Thus, at a given DC voltage at the plus and the negative pole by a corresponding control of the power semiconductor devices V1, V2 of the individual modular switch 20 at the connection P of the inverter 30 an AC voltage can be generated. Conversely, in the case of an AC voltage predetermined at the terminal P, the respective modular switch can be activated by a corresponding control of the power semiconductor components V1, V2 20 a DC voltage between the plus and the negative pole are generated.

The state of charge of the capacitors C in the individual modular switches 20 may differ due to the possible loading and unloading of the capacitors C from each other. As a result, the voltages at the intermediate circuits of the individual phases formed by the respective capacitors C may not be the same. This can lead to reloading between the phases.

By a corresponding control of the power semiconductor components V1, V2, in particular by corresponding switching of the power semiconductor components V1, V2 of the modular switch 20 the individual phases of the inverter 30 a deviation of the voltages at the intermediate circuits of the individual phases formed by the respective capacitors C can be reduced.

This can be achieved, for example, by the time duration during which both power semiconductor components V1, V2 of one of the modular switches 20 are on or off, extended or shortened. By this measure, as explained above, the DC voltage u _dc at the associated capacitor C is increased or decreased.

Alternatively, this can be achieved, for example, by the power semiconductor components V1, V2 of the individual modular switches 20 be switched to redundant switching states, the output side are the same effect.

The remaining, possibly still occurring Umladevorgänge lead to no oscillating currents between the phases. This is because - as has been explained - in the individual modular switches 20 the current i can only flow in one direction. Possible transshipment processes can thus only lead to equalizing currents in one direction, but not to a current reversal and thus not to oscillating currents.

In the 4 is an electrical inverter 40 pictured using the modular switch 20 of the 2 is constructed. It is a so-called multi-level or multi-point converter, which in the present case the 4 has five working points.

The inverter 40 is exemplified for the connection of a three-phase AC voltage. It is understood that the inverter 40 may also be formed in two phases or more generally multiphase.

Every phase of the inverter 40 are four modular switches 20 assigned. The four switches 20 every phase are about their connections 11 . 12 connected in a corresponding manner, as with the inverter 30 of the 3 has already been explained and how this is done in the 4 is shown. Also are the switches 20 each phase in a similar way via the DC link / en 31 . 32 and the inductors 33 connected to the positive pole + and the negative pole - as well as to the connection P.

As has been explained, the terminal voltage u _{a of} each modular switch 20 assume substantially three states: u _a = -u _dc or u _a = u _dc or u _a = 0. Thus, the voltage of each phase of the terminal P relative to the plus or the minus pole can occupy substantially five states, namely: u _a = -2u _dc or u _a = -u _dc or u _a = 0 or u _a = u _dc or u _a = 2u _dc .

Incidentally, with regard to the inverter 40 of the 4 to the explanations of the inverter 30 of the 3 directed.

QUOTES INCLUDE IN THE DESCRIPTION

This list of the documents listed by the applicant has been generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Cited patent literature

• DE 10103031 A1 [0004]

Claims (14)

Modular switch ( 10 . 20 ) for an electrical converter ( 30 . 40 ) with a first series circuit consisting of a first controllable power semiconductor component (V1) and a first diode (D1) and with a second series circuit consisting of a second diode (D2) and a second controllable power semiconductor component (V2), wherein the connection point of the first power semiconductor component ( V1) and the first diode (D1) has a first connection ( 11 ) and the connection point of the second diode (D2) and of the second power semiconductor component (V2) has a second connection ( 12 ) of the modular switch ( 10 . 20 ), and a capacitor (C), wherein the first series circuit and the second series circuit and the capacitor (C) are connected in parallel with each other. Modular switch ( 10 . 20 ) according to claim 1, wherein in the first series circuit, the collector of the first power semiconductor device (V1) and the anode of the first diode (D1) are interconnected, and wherein in the second. Series connection of the emitter of the second power semiconductor device (V2) and the cathode of the second diode (D2) are interconnected. Modular switch ( 10 . 20 ) according to one of the preceding claims, wherein a direct current voltage (u _dc ) is present at the capacitor (C), and between the two terminals ( 11 . 12 ) is a terminal voltage (u _a ) which is either substantially equal to the negative DC voltage or substantially equal to the positive DC voltage or substantially equal to zero. Modular switch ( 10 . 20 ) according to claim 3, wherein the terminal voltage (u _a ) is substantially equal to the negative or positive DC voltage (u _dc ) when both power semiconductor devices (V1, V2) are turned off or turned on. Modular switch ( 10 . 20 ) according to claim 3 or 4, wherein the terminal voltage (u _a ) is substantially equal to zero when one of the two power semiconductor devices (V1, V2) is turned off and the other is turned on. Modular switch ( 10 . 20 ) according to one of the preceding claims, wherein between the terminals ( 11 . 12 ) a current (i) can flow in only one direction. Modular switch ( 20 ) according to one of the preceding claims, wherein the power semiconductor components (V1, V2) each have a freewheeling diode ( 21 ) is connected in parallel. Modular switch ( 20 ) according to one of the preceding claims, wherein the power semiconductor components (V1, V2) each have a diode connected in series to increase the blocking capability. Electrical converter ( 30 . 40 ) for converting a two- or multi-phase AC voltage into a DC voltage or vice versa, with a plurality of modular switches ( 10 . 20 ) according to one of the preceding claims, wherein for each phase of the AC voltage at least two modular switches ( 10 . 20 ) are connected in series. Inverter ( 30 . 40 ) according to claim 9, wherein the series-connected modular switches ( 10 . 20 ) of each phase via at least one DC link inductance ( 31 . 32 ) are connected to a positive pole (+) and a negative pole (-) of the DC voltage. Inverter ( 30 . 40 ) according to claim 9 or 10, wherein a connection point of the modular switches ( 10 . 20 ) each phase via an inductance ( 33 ) are connected to a terminal (P) of the AC voltage. Method for operating an electrical converter ( 30 . 40 ) according to one of claims 9 to 11, wherein the power semiconductor components (V1, V2) of the phases of the converter ( 30 . 40 ) are switched such that deviations of the voltages at the intermediate circuits of the phases formed by the capacitors (C) are reduced. Method according to claim 12, wherein the time duration during which both power semiconductor components (V1, V2) of one of the modular switches ( 20 ) are on or off, extended or shortened. Method according to claim 12, wherein the power semiconductor components (V1, V2) of one of the modular switches ( 20 ) are switched to switching states that have the same effect on the output side.

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